1. Field of the Invention
The present invention relates to a switch configuration for key-entry operation, and more particularly, to a key-entry switch device (hereinafter referred to as a key switch) preferably used for a keyboard incorporated, as an input device in electronic equipment. The present invention also relates to a keyboard provided with key switches.
2. Description of the Related Art
In a portable electronic apparatus, such as a notebook or palm-top personal computer, various arts have been proposed to improve the operability of the key switch for realizing a reduction in the height of a package including the keyboard. Especially, to reduce the height of the keyboard including a plurality of key switches for a key-entry operation, it is necessary to reduce the height of a key switch when it is depressed (switch-on) as well as in an inoperative position (switch-off) while maintaining a predetermined amount of stroke of the key switch large enough to provide a certain level of operability of the key switch.
Conventionally, a key-switch used for a thinner or low-profile-type keyboard includes a base panel; a key top arranged above the base panel; a pair of link members interlocked to each other, to support the key top above the base panel and direct the key top in a vertical direction; a switch mechanism capable of opening and closing a contact section at a position corresponding to the key top. A pair of link members are assembled together into a reverse V-shape as seen from a lateral direction (or in a side view), engaged with the base panel slidably at the first end region, engaged each other at the second end region and pivotally joined to the key top, which may be referred to as a gear-link type (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 11-3628 (JP-A-11-3628)). Also, a new gear-link type constitution for a low-profile-type keyboard with increased stroke has been proposed (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 2006-049274 (JP-A-2006-049274)). This type includes a wall portion extending from a plate member of the base panel, the sliding parts of the pair of link members are slidably engaged with the guide grooves of the wall portions, and the pivoting shafts of the link members are pivotally joined to the pivot support sections of the key top.
In the gear-link type described in JP-A-2006-049274, before attaching the key top to the pair of link members, only four wall portions of the base panel hold the pair of link members. Namely, the pair of link members is held between the wall portions. However, a certain amount of clearance must be provided between the wall portions and the pair of link members. Therefore, the pair of link-members is not immovably retained by the wall portions.
A relative displacement of the pair of link members may occur due to accidental contact of the key top with the pair of link members upon attachment of the key top. As a result, in some cases, the gear portions of the pair of link members that have engaged with each other disengage from one another. The key top attached to the pair of link members which have been relatively displaced exerts an unreasonable amount of force upon the link members, Consequently, in the worst case, the sliding parts of the link members may be disengaged from the guide grooves of the wall portions.
When an operator attaches the key top to the pair of link members, a first pair of pivot support sections provided on one side of the key top is first engaged with corresponding pivoting shafts of the pair of link members, and thereafter engages a second pivot support sections provided on the other side of the key top with the corresponding pivoting shafts of the pair of link members. In this assembly method, there is the fear that the pair of link members are undesirably damaged.
It is difficult for a user to prevent attaching the key top to the pair of link members in the undesirable assembly method as mentioned above, in the gear-link type as described in JP-A-2006-049274.